TODO

   1 ************************************************************************
   2 * Official mandoc TODO.
   3 * $Id: TODO,v 1.273 2018/10/02 14:56:47 schwarze Exp $
   4 ************************************************************************
   5
   6 Many issues are annotated for difficulty as follows:
   7
   8  - loc = locality of the issue
   9     *    single file issue, affects file only, or very few
  10     **   single module issue, affects several files of one module
  11     ***  cross-module issue, significantly impacts multiple modules
  12          and may require substantial changes to internal interfaces
  13  - exist = difficulty of the existing code in this area
  14     *    affected code is straightforward and easy to read and change
  15     **   affected code is somewhat complex, but once you understand
  16          the design, not particularly difficult to understand
  17     ***  affected code uses a special, exceptionally tricky design
  18  - algo = difficulty of the new algorithm to be written
  19     *    the required logic and code is straightforward
  20     **   the required logic is somewhat complex and needs a careful design
  21     ***  the required logic is exceptionally tricky,
  22          maybe an approach to solve that is not even known yet
  23  - size = the amount of code to be written or changed
  24     *    a small number of lines (at most 100, usually much less)
  25     **   a considerable amount of code (several dozen to a few hundred)
  26     ***  a large amount of code (many hundreds, maybe thousands)
  27  - imp = importance of the issue
  28     *    mostly for completeness
  29     **   would be nice to have
  30     ***  issue causes considerable inconvenience
  31
  32 Obviously, as the issues have not been solved yet, these annotations
  33 are mere guesses, and some may be wrong.
  34
  35 ************************************************************************
  36 * missing features
  37 ************************************************************************
  38
  39 --- missing roff features ----------------------------------------------
  40
  41 - .ad (adjust margins)
  42   .ad l -- adjust left margin only (flush left)
  43   .ad r -- adjust right margin only (flush right)
  44   .ad c -- center text on line
  45   .ad b -- adjust both margins (alias: .ad n)
  46   .na   -- temporarily disable adjustment without changing the mode
  47   .ad   -- re-enable adjustment without changing the mode
  48   Adjustment mode is ignored while in no-fill mode (.nf).
  49   loc ***  exist ***  algo **  size **  imp **  (parser reorg would help)
  50
  51 - .fc (field control)
  52   found by naddy@ in xloadimage(1)
  53   loc **  exist ***  algo *  size *  imp *
  54
  55 - .ns (no-space mode) occurs in xine-config(1)
  56   when implementing this, also let .TH set it
  57   reported by brad@  Sat, 15 Jan 2011 15:45:23 -0500
  58   loc ***  exist ***  algo ***  size **  imp *
  59
  60 - \w'' improve width measurements
  61   would not be very useful without an expression parser, see below
  62   needed for Tcl_NewStringObj(3) via wiz@  Wed, 5 Mar 2014 22:27:43 +0100
  63   loc **  exist ***  algo ***  size *  imp ***
  64
  65 - \\ in high-level macro arguments
  66   Currently, \\ is expanded in two situations:
  67   1) macro and string definition (roff.c setstrn())
  68   2) macro argument parsing (mandoc.c mandoc_getarg())
  69   For user defined macros, the second happens in time because of ROFF_REPARSE.
  70   But for standard high-level macros, it only happens after entering the
  71   high level parsers, which is too late because the code doesn't get
  72   back to roff.c roff_res() from that point.  Because this requires
  73   distinguishing requests, user-defined macros and standard macros
  74   on the roff_res() level, it is hard to solve without the parser reorg.
  75   Found by naddy@ in devel/cutils cobfusc(1)  Mon, 16 Feb 2015 19:10:52 +0100
  76   loc ***  exist ***  algo ***  size **  imp *
  77
  78 - check for missing roff escape sequences, implement those that are
  79   trivial even if not usually appearing in manual pages, gracefully
  80   ignore the non-trivial ones, document what they are supposed to do
  81   and what mandoc does instead
  82   loc *  exist **  algo *  size *  imp *
  83
  84 --- missing mdoc features ----------------------------------------------
  85
  86 - .Bl -column .Xo support is missing
  87   ultimate goal:
  88   restore .Xr and .Dv to
  89   lib/libc/compat-43/sigvec.3
  90   lib/libc/gen/signal.3
  91   lib/libc/sys/sigaction.2
  92   loc *  exist ***  algo ***  size *  imp **
  93
  94 - edge case: decide how to deal with blk_full bad nesting, e.g.
  95   .Sh .Nm .Bk .Nm .Ek .Sh found by jmc@ in ssh-keygen(1)
  96   from jmc@  Wed, 14 Jul 2010 18:10:32 +0100
  97   loc *  exist ***  algo ***  size **  imp **
  98
  99 - .Bd -centered implies -filled, not -unfilled, which is not
 100   easy to implement; it requires code similar to .ce, which
 101   we don't have either.
 102   Besides, groff has bug causing text right *before* .Bd -centered
 103   to be centered as well.
 104   loc ***  exist ***  algo **  size **  imp **  (parser reorg would help)
 105
 106 - .Bd -filled should not be the same as .Bd -ragged, but align both
 107   the left and right margin.  In groff, it is implemented in terms
 108   of .ad b, which we don't have either.  Found in cksum(1).
 109   loc ***  exist ***  algo **  size **  imp **  (parser reorg would help)
 110
 111 - implement blank `Bl -column', such as
 112   .Bl -column
 113   .It foo Ta bar
 114   .El
 115   loc *  exist ***  algo ***  size *  imp *
 116
 117 - explicitly disallow nested `Bl -column', which would clobber internal
 118   flags defined for struct mdoc_macro
 119   loc *  exist *  algo *  size *  imp **
 120
 121 - In .Bl -column .It, the end of the line probably has to be regarded
 122   as an implicit .Ta, if there could be one, see the following mildly
 123   ugly code from login.conf(5):
 124     .Bl -column minpasswordlen program xetcxmotd
 125     .It path Ta path Ta value of Dv _PATH_DEFPATH
 126     .br
 127     Default search path.
 128   reported by Michal Mazurek <akfaew at jasminek dot net>
 129   via jmc@ Thu, 7 Apr 2011 16:00:53 +0059
 130   loc *  exist ***  algo **  size *  imp **
 131
 132 - inside `.Bl -column' phrases, punctuation is handled like normal
 133   text, e.g. `.Bl -column .It Fl x . Ta ...' should give "-x -."
 134
 135 - inside `.Bl -column' phrases, TERMP_IGNDELIM handling by `Pf'
 136   is not safe, e.g. `.Bl -column .It Pf a b .' gives "ab."
 137   but should give "ab ."
 138
 139 - prohibit `Nm' from having non-text HEAD children
 140   (e.g., NetBSD mDNSShared/dns-sd.1)
 141   (mdoc_html.c and mdoc_term.c `Nm' handlers can be slightly simplified)
 142
 143 - support translated section names
 144   e.g. x11/scrotwm scrotwm_es.1:21:2: error: NAME section must be first
 145   that one uses NOMBRE because it is spanish...
 146   deraadt tends to think that section-dependent macro behaviour
 147   is a bad idea in the first place, so this may be irrelevant
 148   loc **  exist **  algo **  size *  imp **
 149
 150 - When there is free text in the SYNOPSIS and that free text contains
 151   the .Nm macro, groff somehow understands to treat the .Nm as an in-line
 152   macro, while mandoc treats it as a block macro and breaks the line.
 153   No idea how the logic for distinguishing in-line and block instances
 154   should be, needs investigation.
 155   uqs@  Thu, 2 Jun 2011 11:03:51 +0200
 156   uqs@  Thu, 2 Jun 2011 11:33:35 +0200
 157   loc *  exist **  algo ***  size *  imp **
 158
 159 --- missing man features -----------------------------------------------
 160
 161 - groff_www(7) .MTO and .URL
 162   These macros were used by the GNU grep(1) man page.
 163   The groff_www(7) manual page itself uses them, too.
 164   We should probably *not* add them to mandoc.
 165   Just mentioning this here to keep track of the abuse.
 166   Laura Morales <lauretas at mail dot com> 20 Apr 2018 07:33:02 +0200
 167   loc **  exist *  algo *  size **  imp *
 168
 169 --- missing tbl features -----------------------------------------------
 170
 171 - the "s" layout column specifier is used for placement of data
 172   into columns, but ignored during column width calculations
 173   synaptics(4) found by tedu@  Mon, 17 Aug 2015 21:17:42 -0400
 174   loc *  exist **  algo ***  size *  imp **
 175
 176 - vertical centering in cells vertically spanned with ^
 177   pali dot rohar at gmail dot com 16 Jul 2018 13:03:35 +0200
 178   loc *  exist ***  algo ***  size **  imp *
 179
 180 - support mdoc(7) and man(7) macros inside tbl(7) code;
 181   probably requires the parser reorg and letting tbl(7)
 182   use roff_node such that macro sets can mix;
 183   informed by bapt@ that FreeBSD needs this: 3 Jan 2015 23:32:23 +0100
 184   loc ***  exist **  algo ***  size **  imp ***
 185
 186 - look at the POSIX manuals in the books/man-pages-posix port,
 187   they use some unsupported tbl(7) features.
 188   loc *  exist **  algo **  size **  imp ***
 189
 190 - look what Joerg Schilling manual pages use
 191   Thu, 19 Mar 2015 18:31:48 +0100
 192
 193 - use Unicode U+2500 to U+256C for table borders
 194   in tbl(7) -Tutf-8 output
 195   suggested by bentley@  Tue, 14 Oct 2014 04:10:55 -0600
 196   loc *  exist **  algo *  size *  imp **
 197
 198 - implement horizontal and vertical alignment in HTML output
 199   pali dot rohar at gmail dot com 16 Jul 2018 13:03:35 +0200
 200   loc *  exist *  algo *  size *  imp ***
 201
 202 - implement cell spanning in HTML output
 203   pali dot rohar at gmail dot com 16 Jul 2018 13:03:35 +0200
 204   loc *  exist *  algo **  size **  imp **
 205
 206 - implement table borders in HTML output
 207   pali dot rohar at gmail dot com 16 Jul 2018 13:03:35 +0200
 208   loc *  exist *  algo **  size **  imp **
 209
 210 --- missing eqn features -----------------------------------------------
 211
 212 - In a matrix, break the output line after each matrix line.
 213   Found in the discussion at CDBUG 2015.
 214   Suggested by Avi Weinstock.
 215   loc *  exist *  algo *  size *  imp **
 216
 217 - The "size" keyword is parsed, but ignored by the formatter.
 218   loc *  exist *  algo *  size *  imp *
 219
 220 - The spacing characters `~', `^', and tab are currently ignored,
 221   see User's Guide (Second Edition) page 2 section 4.
 222   loc *  exist *  algo **  size *  imp **
 223
 224 - Mark and lineup are parsed and ignored,
 225   see User's Guide (Second Edition) page 5 section 15.
 226   loc **  exist **  algo **  size **  imp **
 227
 228 - GNU eqn converts some operators to special characters, for example,
 229   input HYPHEN-MINUS becomes output \(mi, unless it is part of a
 230   quoted word.  mandoc(1) only does this when the operator is
 231   surrounded by blanks, not when it is part of an unquoted word.
 232   Also, check whether there are more such cases (e.g., +?).
 233   reported by bentley@  20 Jun 2017 02:04:29 -0600
 234   loc *  exist **  algo **  size *  imp *
 235
 236 - Primes, opprime, and '
 237   bentley@  Thu, 13 Jul 2017 23:14:20 -0600
 238
 239 --- missing misc features ----------------------------------------------
 240
 241 - man -ks 1,8 route; kn@ Jul 13, 2018 orally
 242
 243 - italic correction (\/) in PostScript mode
 244   Werner LEMBERG on groff at gnu dot org  Sun, 10 Nov 2013 12:47:46
 245   loc **  exist **  algo *  size *  imp *
 246
 247 - change the default PAGER to more -Es and use the pager
 248   even for apropos title line output; req by bapt@
 249   loc *  exist *  algo *  size *  imp ***
 250
 251 - clean up escape sequence handling, creating three classes:
 252   (1) fully implemented, or parsed and ignored without loss of content
 253   (2) unimplemented, potentially causing loss of content
 254       or serious mangling of formatting (e.g. \n) -> ERROR
 255       see textproc/mgdiff(1) for nice examples
 256   (3) undefined, just output the character -> perhaps WARNING
 257   loc ***  exist **  algo **  size **  imp *** (parser reorg helps)
 258
 259 - kettenis wants base roff, ms, and me  Fri, 1 Jan 2010 22:13:15 +0100 (CET)
 260   loc **  exist **  algo **  size ***  imp *
 261
 262 --- compatibility checks -----------------------------------------------
 263
 264 - is .Bk implemented correctly in modern groff?
 265   sobrado@  Tue, 19 Apr 2011 22:12:55 +0200
 266
 267 - compare output to Heirloom roff, Solaris roff, and
 268   http://repo.or.cz/w/neatroff.git  http://litcave.rudi.ir/
 269
 270 - look at AT&T DWB http://www2.research.att.com/sw/download
 271   Carsten Kunze <carsten dot kunze at arcor dot de> has patches
 272   Mon, 4 Aug 2014 17:01:28 +0200
 273   ported version: https://github.com/n-t-roff/DWB3.3
 274   Carsten Kunze  Wed, 22 Apr 2015 11:21:43 +0200
 275
 276 - look at pages generated from reStructeredText, e.g. devel/mercurial hg(1)
 277   These are a weird mixture of man(7) and custom autogenerated low-level
 278   roff stuff.  Figure out to what extent we can cope.
 279   For details, see http://docutils.sourceforge.net/rst.html
 280   noted by stsp@  Sat, 24 Apr 2010 09:17:55 +0200
 281   reminded by nicm@  Mon, 3 May 2010 09:52:41 +0100
 282
 283 - look at pages generated from ronn(1) github.com/rtomayko/ronn
 284   (based on markdown)
 285
 286 - look at pages generated from Texinfo source by yat2m, e.g. security/gnupg
 287   First impression is not that bad.
 288
 289 - look at pages generated by pandoc; see
 290   https://github.com/jgm/pandoc/blob/master/src/Text/Pandoc/Writers/Man.hs
 291   porting planned by kili@  Thu, 19 Jun 2014 19:46:28 +0200
 292
 293 - check compatibility with Plan9:
 294   http://swtch.com/usr/local/plan9/tmac/tmac.an
 295   http://swtch.com/plan9port/man/man7/man.html
 296   "Anthony J. Bentley" <anthonyjbentley@gmail.com> 28 Dec 2010 21:58:40 -0700
 297
 298 - check compatibility with COHERENT troff:
 299   http://www.nesssoftware.com/home/mwc/source.php
 300
 301 - check compatibility with the man(7) formatter
 302   https://raw.githubusercontent.com/rofl0r/hardcore-utils/master/man.c
 303
 304 - check compatibility with
 305   http://ikiwiki.info/plugins/contrib/mandoc/
 306   https://github.com/schmonz/ikiwiki/compare/mandoc
 307   Amitai Schlair  Mon, 19 May 2014 14:05:53 -0400
 308
 309 - check features of the Slackware man.conf(5) format
 310   Carsten Kunze  Wed, 11 Mar 2015 17:57:24 +0100
 311
 312 ************************************************************************
 313 * formatting issues: ugly output
 314 ************************************************************************
 315
 316 - revisit empty in-line macros
 317   look at the difference between "Em x Em ." and "Sq x Em ."
 318   Carsten Kunze  Fri, 12 Dec 2014 00:15:41 +0100
 319   loc *** exist *** algo *** size * imp **
 320
 321 - a column list with blank `Ta' cells triggers a spurious
 322   start-with-whitespace printing of a newline
 323
 324 - In .Bl -column, .It a<tab>"b<tab>c"
 325   shows the quotes in groff, but not in mandoc
 326   loc * exist *** algo ** size * imp **
 327
 328 - In .Bl -column,
 329   .It Em Authentication<tab>Key Length
 330   ought to render "Key Length" with emphasis, too,
 331   see OpenBSD iked.conf(5).
 332   reported again Nicolas Joly via wiz@ Wed, 12 Oct 2011 00:20:00 +0200
 333   loc *  exist ***  algo ***  size **  imp ***
 334
 335 - empty phrases in .Bl column produce too few blanks
 336   try e.g. .Bl -column It Ta Ta
 337   reported by millert Fri, 02 Apr 2010 16:13:46 -0400
 338   loc *  exist ***  algo ***  size *  imp **
 339
 340 - .%T can have trailing punctuation.  Currently, it puts the trailing
 341   punctuation into a trailing MDOC_TEXT element inside its own scope.
 342   That element should rather be outside its scope, such that the
 343   punctuation does not get underlines.  This is not trivial to
 344   implement because .%T then needs some features of in_line_eoln() -
 345   slurp all arguments into one single text element - and one feature
 346   of in_line() - put trailing punctuation out of scope.
 347   Found in mount_nfs(8) and exports(5), search for "Appendix".
 348   loc **  exist **  algo ***  size *  imp **
 349
 350 - Trailing punctuation after .%T triggers EOS spacing, at least
 351   outside .Rs (eek!).  Simply setting ARGSFL_DELIM for .%T is not
 352   the right solution, it sends mandoc into an endless loop.
 353   reported by Nicolas Joly  Sat, 17 Nov 2012 11:49:54 +0100
 354   loc *  exist **  algo **  size *  imp **
 355
 356 - global variables in the SYNOPSIS of section 3 pages
 357   .Vt vs .Vt/.Va vs .Ft/.Va vs .Ft/.Fa ...
 358   from kristaps@  Tue, 08 Jun 2010 11:13:32 +0200
 359
 360 - implicit whitespace around inline equations
 361   example code:  where '$times$' denotes matrix multiplication
 362   must not have an HTML line break, nor a blank, before <math>
 363   partial solution: html.c {"math", HTML_NLINSIDE | HTML_INDENT},
 364   bentley@  Thu, 13 Jul 2017 19:00:59 -0600
 365
 366 - in enclosures, mandoc sometimes fancies a bogus end of sentence
 367   reminded by jmc@  Thu, 23 Sep 2010 18:13:39 +0059
 368   loc *  exist **  algo ***  size *  imp ***
 369
 370 - a line starting with "\fB something" counts as starting with whitespace
 371   and triggers a line break; found in audio/normalize-mp3(1)
 372   loc **  exist *  algo **  size *  imp **
 373
 374 - formatting /usr/local/man/man1/latex2man.1 with groff and mandoc
 375   reveals lots of bugs both in groff and mandoc...
 376   reported by bentley@  Wed, 22 May 2013 23:49:30 -0600
 377
 378 --- PostScript and PDF issues ------------------------------------------
 379
 380 - PDF output doesn't use a monospaced font for .Bd -literal
 381   Example: "mandoc -Tpdf afterboot.8 > output.pdf && pdfviewer output.pdf".
 382   Search the text "Routing tables".
 383   Also check what PostScript mode does when fixing this.
 384   reported by juanfra@ Wed, 04 Jun 2014 21:44:58 +0200
 385   instructions from juanfra@  Wed, 11 Jun 2014 02:21:01 +0200
 386     add a new <</Type /Font>> block to the PDF files with /BaseFont /Courier
 387     and change the /Name from /F0 to the new font (/F5 (?)).
 388   re-reported by tb@ Mon, 16 Mar 2015 16:47:21 +0100
 389   loc *  exist **  algo **  size *  imp **
 390
 391 --- HTML issues --------------------------------------------------------
 392
 393 - wrap Sh and Ss content into <div>
 394   Laura Morales <lauretas at mail dot com> 21 Apr 2018 18:10:48 +0200
 395   (Evaluate whether this is really useful and has no adverse
 396    side effects before implementing; if it is possible,
 397    it does seem cleaner.)
 398   loc **  exist **  algo *  size *  imp ***
 399
 400 - format ".IP *" etc. as <ul> rather than <dl>
 401   https://github.com/Debian/debiman/issues/67
 402   loc ** exist ** algo ** size * imp ***
 403
 404 - .Bf at the beginning of a paragraph inserts a bogus 1ex horizontal
 405   space, see for example random(3).  Introduced in
 406   http://mdocml.bsd.lv/cgi-bin/cvsweb/mdoc_html.c.diff?r1=1.91&r2=1.92
 407   reported by deraadt@ Mon, 28 Sep 2015 20:14:13 -0600 (MDT)
 408   loc **  exist **  algo **  size *  imp *
 409
 410 - jsg on icb, Nov 3, 2014:
 411   try to guess Xr in man(7) for hyperlinking
 412   and render them with <a class="Xr" href=...>
 413   https://github.com/Debian/debiman/issues/15
 414   loc *  exist *  algo **  size **  imp **
 415
 416 - The tables used to render the three-part page headers actually force
 417   the width of the <body> to the max-width given for <html>.
 418   Not yet sure how to fix that...
 419   Observed by an Anonymous Coward on undeadly.org:
 420   http://undeadly.org/cgi?action=article&sid=20140925064244&pid=1
 421   loc *  exist *  algo **  size *  imp ***
 422
 423 - generate <img> tags in HTML
 424   idea from florian@  Tue, 7 Apr 2015 00:26:28 +0000
 425   may be possible to implement with .Lk img://something.png alt_text
 426
 427 - check https://github.com/trentm/mdocml
 428
 429 ************************************************************************
 430 * formatting issues: gratuitous differences
 431 ************************************************************************
 432
 433 - .Fn reopens a new scope after punctuation in mandoc,
 434   but closes its scope for good in groff.
 435   Do we want to change mandoc or groff?
 436   Steffen Nurpmeso  Sat, 08 Nov 2014 13:34:59 +0100
 437   loc *  exist **  algo **  size *  imp **
 438
 439 - In .Bl -enum -width 0n, groff continues one the same line after
 440   the number, mandoc breaks the line.
 441   mail to kristaps@  Mon, 20 Jul 2009 02:21:39 +0200
 442   loc *  exist **  algo **  size *  imp **
 443
 444 - .Pp between two .It in .Bl -column should produce one,
 445   not two blank lines, see e.g. login.conf(5).
 446   reported by jmc@  Sun, 17 Apr 2011 14:04:58 +0059
 447   reported again by sthen@  Wed, 18 Jan 2012 02:09:39 +0000 (UTC)
 448   loc *  exist ***  algo **  size *  imp **
 449
 450 - If the *first* line after .It is .Pp, break the line right after
 451   the tag, do not pad with space characters before breaking.
 452   See the description of the a, c, and i commands in sed(1).
 453   loc *  exist **  algo **  size *  imp **
 454
 455 - If the first line after .It is .D1, do not assert a blank line
 456   in between, see for example tmux(1).
 457   reported by nicm@  13 Jan 2011 00:18:57 +0000
 458   loc *  exist **  algo **  size *  imp **
 459
 460 - Trailing punctuation after .It should trigger EOS spacing.
 461   reported by Nicolas Joly  Sat, 17 Nov 2012 11:49:54 +0100
 462   Probably, this should be fixed somewhere in termp_it_pre(), not sure.
 463   loc *  exist **  algo **  size *  imp **
 464
 465 - When the -width string contains macros, the macros must be rendered
 466   before measuring the width, for example
 467     .Bl -tag -width ".Dv message"
 468   in magic(5), located in src/usr.bin/file, is the same
 469   as -width 7n, not -width 11n.
 470   The same applies to .Bl -column column widths;
 471   reported again by Nicolas Joly Thu, 1 Mar 2012 13:41:26 +0100 via wiz@ 5 Mar
 472   reported again by Franco Fichtner Fri, 27 Sep 2013 21:02:28 +0200
 473   reported again by Bruce Evans Fri, 17 Feb 2017 21:22:44 +0100 via bapt@
 474   loc ***  exist ***  algo ***  size **  imp ***
 475   An easy partial fix would be to just skip the first word if it starts
 476   with a dot, including any following white space, when measuring.
 477   loc *  exist *  algo *  size *  imp ***
 478
 479 - The \& zero-width character counts as output.
 480   That is, when it is alone on a line between two .Pp,
 481   we want three blank lines, not two as in mandoc.
 482   loc **  exist **  algo **  size *  imp **
 483
 484 - Sequences of multiple man(7) paragraphs (.PP, .IP) interspersed
 485   with .ps and .nf/.fi produce execessive blank lines, see libJudy
 486   and graphics/dcmtk.  The parser reorg may help with this.
 487
 488 - trailing whitespace must be ignored even when followed by a font escape,
 489   see for example
 490     makes
 491     \fBdig \fR
 492     operate in batch mode
 493   in dig(1).
 494   loc **  exist **  algo **  size *  imp **
 495
 496 ************************************************************************
 497 * warning issues
 498 ************************************************************************
 499
 500 - When a man(1) command returns no result and there was an -S
 501   argument, check the -S argument against the list of valid
 502   architectures and say "Unknown architecture AAA" rather than
 503   "No entry for NNN in the manual" if there is no match.
 504   Requires moving the lists of valid architectures out of
 505   mdoc_validate.c such that they can be used by main.c.
 506   Discussed with jmc@ 10 Aug 2018 19:20:12 +0100.
 507   loc **  exist *  algo *  size *  imp **
 508
 509 - warn about duplicate .Sh/.Ss heads
 510   gre(4): Rename duplicate sections 20 Apr 2018 15:27:33 +0200
 511   loc *  exist *  algo *  size *  imp **
 512
 513 - style message about macros inside .Bd -literal and .Dl, in particular
 514   font changing macros like .Cm, .Ar, .Fa (from the mdoclint TODO)
 515
 516 - style message about mismatches between the section number in the
 517   file name (if it is known) and the section number in .Dt
 518   (from the mdoclint TODO)
 519
 520 - style message about NULL without .Dv (from the mdoclint TODO)
 521
 522 - style message about error constants without .Er (from the mdoclint TODO)
 523
 524 - warn when .Sh or .Ss contain other macros
 525   Steffen Nurpmeso, savannah.gnu.org/bugs/index.php?45034
 526   loc *  exist *  algo *  size *  imp **
 527
 528 - style message about violations of the convention
 529   .An name Aq Mt localpart@domain in AUTHORS (from the mdoclint TODO)
 530
 531 - warn about attempts to call non-callable macros
 532   Steffen Nurpmeso  Tue, 11 Nov 2014 22:55:16 +0100
 533   Note that formatting is inconsistent in groff.
 534   .Fn Po prints "Po()", .Ar Sh prints "file ..." and no "Sh".
 535   Relatively hard because the relevant code is scattered
 536   all over mdoc_macro.c and all subtly different.
 537   loc **  exist **  algo **  size **  imp **
 538
 539 - style message about suspicious uses of - vs. \- vs. \(mi
 540   e.g. -1 is likely wrong (from the mdoclint TODO)
 541
 542 - warn about punctuation - e.g. ',' and ';' - at the beginning
 543   of a text line, if it is likely intended to follow the preceding
 544   output without intervening whitespace, in particular after a
 545   macro line (from the mdoclint TODO)
 546
 547 - mandoc_special does not really check the escape sequence,
 548   but just the overall format
 549   loc **  exist **  algo ***  size **  imp **
 550
 551 - makewhatis -p complains about language subdirectories:
 552   /usr/local/man//ru: Unknown directory part
 553
 554
 555 ************************************************************************
 556 * documentation issues
 557 ************************************************************************
 558
 559 - dashes, hyphens, and minus signs in manual pages
 560   jmc@ Fri, 28 Mar 2014 07:19:27 +0000
 561
 562 - mark macros as: page structure domain, manual domain, general text domain
 563   is this useful?
 564
 565 - mention /usr/share/misc/mdoc.template in mdoc(7)?
 566
 567 - Is all the content from http://www.std.com/obi/BSD/doc/usd/28.tbl/tbl
 568   covered in tbl(7)?
 569
 570 ************************************************************************
 571 * performance issues
 572 ************************************************************************
 573
 574 - the PDF file is HUGE: this can be reduced by using relative offsets
 575
 576 ************************************************************************
 577 * structural issues
 578 ************************************************************************
 579
 580 - POSIX says in the documentation of sysconf(3) that PATH_MAX
 581   is allowed to be so large that it is a bad idea to use it
 582   for sizing static buffers.  So use dynamic buffers throughout.
 583   See the file test-PATH_MAX.c for details.
 584   Found by Aaron M. Ucko in the GNU Hurd via Bdale Garbee,
 585   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=829624
 586
 587 - We use the input line number at several places to distinguish
 588   same-line from different-line input.  That plainly doesn't work
 589   with user-defined macros, leading to random breakage.
 590
 591 - Is it possible to further simplify ENDBODY_SPACE?
 592
 593 - Find better ways to prevent endless loops
 594   in roff(7) macro and string expansion.
 595
 596 - make buffers for parsing functions const
 597   christos@ via wiz@  Fri, 18 Dec 2015 17:10:01 +0100
 598
 599 - struct mparse refactoring
 600   Steffen Nurpmeso  Thu, 04 Sep 2014 12:50:00 +0200
 601
 602 ************************************************************************
 603 * CGI issues
 604 ************************************************************************
 605
 606  - Enable HTTP compression by detecting gzip encoding and filtering
 607    output through libz.
 608  - Privilege separation (see OpenSSH).
 609  - Enable caching support via HTTP 304 and If-Modified-Since.
 610  - Have Mac OSX systems automatically disable -static compilation of the
 611    CGI: -static isn't supported.
 612
 613 ************************************************************************
 614 * to improve in the groff_mdoc(7) macros
 615 ************************************************************************
 616
 617 - .Cd # arch1, arch2 in section 4 pages:
 618   find better way to indicate multiple architectures, maybe:
 619   allow .Dt vgafb 4 "macppc sparc64"
 620   already shown as "Device Drivers Manual (macppc sparc64)"
 621   for apropos, make that "vgafb(4) - macppc # sparc64" instead of "- all"
 622   groff can be made to show multiple arches, too, but it is
 623   tedious to do the string parsing in roff code...
 624   jmc@ 23 Apr 2018 07:24:52 +0100 [man for vgafb(4)...]
 625   loc **  exist **  algo *  size *  imp ***
 626
 627 - use uname(1) to set doc-default-operating-system at install time
 628   tobimensch  Mon, 1 Dec 2014 00:25:07 +0100
 629
 630 - apostrophe (39), circumflex (94), grave (96), tilde (126)
 631   in manuals: \(aq, \(ha, \`, \(ti
 632   Re: [Groff] ASCII Minus Sign in man Pages.
 633   bentley@ 26 Apr 2017 10:02:06 -0600
 634   Do we need to fix existing manuals?
 635   Do we need to fix the definition of the mdoc(7) language?